It is the long-range purpose of this project to study the control mechanisms important in regulating protein synthesis in normal and malignant mammalian cells. A. Transcription of and translation by tRNA is being studied by comparing isoaccepting tRNA chromatographic profiles of normal and tumorous tissue. Primarily rat and mouse liver tRNA is being compared with tRNA from rat and mouse tumors, particularly rat hepatomas and a carefully selected series of immunoglobulin secreting mouse plasma cell tumors. Of special interest is the origin, structure and function of a species of phenylalanyl-tRNA found only in certain rat tumors. B. The synthesis and structure of IgA half molecules, mouse IgA myeloma proteins made up of one light chain disulfide bonded to one unusually short heavy chain is also of major interest, particularly to determine if these molecules represent a normal IgA subclass or products of aberrant or imcomplete synthesis at the DNA, RNA or protein synthetic level.